U.S. patent application number 12/811664 was filed with the patent office on 2010-11-11 for method and composition for preparation of hydrogen peroxide.
This patent application is currently assigned to OCI COMPANY LTD.. Invention is credited to Do Sun Baik, Rae Sung Chung, Deok Yun Kim, Yong Il Kim, Sun Ki Seo, Tae Hee Shin, Se In Yang, Kyung Keun Yoo.
Application Number | 20100284901 12/811664 |
Document ID | / |
Family ID | 41570450 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100284901 |
Kind Code |
A1 |
Yang; Se In ; et
al. |
November 11, 2010 |
METHOD AND COMPOSITION FOR PREPARATION OF HYDROGEN PEROXIDE
Abstract
The present invention relates to a method for the preparation of
hydrogen peroxide through a continuous process, extracting hydrogen
peroxide produced from reduction and oxidation of a working
solution and recycling the oxidized working solution back to the
reduction process, wherein the composition of the working solution,
i.e. the composition of 2-alkylanthraquinone and
2-tetrahydroalkylanthraquinone, is optimized to increase the
solubility of the quinones and to improve the reaction rate. The
working solution comprises 2-alkylanthraquinone,
2-tetrahydroalkylanthraquinone and an organic solvent, wherein
65-95 mol % of the alkyl group of 2-alkylanthraquinone and
2-tetrahydroalkylanthraquinone is amyl and the remaining 5-35 mol %
of the alkyl group is ethyl, and the molar ratio of
2-alkylanthraquinone to 2-tetrahydroalkylanthraquinone is from 4:6
to 1:9.
Inventors: |
Yang; Se In; (Gyeonggi-do,
KR) ; Yoo; Kyung Keun; (Seoul, KR) ; Kim; Yong
Il; (Incheon, KR) ; Shin; Tae Hee; (Seoul,
KR) ; Kim; Deok Yun; (Gyeonggi-do, KR) ; Seo;
Sun Ki; ( Jeollabuk-do, KR) ; Chung; Rae Sung;
(Jeollabuk-do, KR) ; Baik; Do Sun; ( Jeollabuk-do,
KR) |
Correspondence
Address: |
LOWE HAUPTMAN HAM & BERNER, LLP
1700 DIAGONAL ROAD, SUITE 300
ALEXANDRIA
VA
22314
US
|
Assignee: |
OCI COMPANY LTD.
Seoul
KR
|
Family ID: |
41570450 |
Appl. No.: |
12/811664 |
Filed: |
March 6, 2009 |
PCT Filed: |
March 6, 2009 |
PCT NO: |
PCT/KR2009/001135 |
371 Date: |
July 2, 2010 |
Current U.S.
Class: |
423/588 ;
252/182.12 |
Current CPC
Class: |
C01B 15/023
20130101 |
Class at
Publication: |
423/588 ;
252/182.12 |
International
Class: |
C01B 15/023 20060101
C01B015/023; C09K 3/00 20060101 C09K003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2008 |
KR |
10-2008-0071270 |
Claims
1. A method for preparation of hydrogen peroxide through an
anthraquinone recycle process of reducing and oxidizing a working
solution comprising 2-alkylanthraquinone,
2-tetrahydroalkylanthraquinone and an organic solvent, wherein
65-95 mol % of the alkyl group of 2-alkylanthraquinone and
2-tetrahydroalkylanthraquinone is amyl and the remaining 5-35 mol %
of the alkyl group is ethyl, and the molar ratio of
2-alkylanthraquinone to 2-tetrahydroalkylanthraquinone is from 4:6
to 1:9.
2. The method for preparation of hydrogen peroxide according to
claim 1, wherein the amyl group comprises tert-amyl and
iso-sec-amyl at a molar ratio of 7:3 to 9:1.
3. The method for preparation of hydrogen peroxide according to
claim 1, wherein the inert ingredients produced from the side
reaction of 2-alkylanthraquinone are included in the working
solution in an amount of 3-20 wt %.
4. The method for preparation of hydrogen peroxide according to
claim 1, wherein water is further contained in the working solution
in an amount of 0.05-0.5 wt %.
5. The method for preparation of hydrogen peroxide according to
claim 1, wherein the working solution comprises 17-34 wt % of
2-alkylanthraquinone and 2-tetrahydroalkylanthraquinone.
6. The method for preparation of hydrogen peroxide according to
claim 1, wherein the degree of hydrogenation during the reduction
of the working solution is controlled to be 70-100 mol % on the
basis of 2-tetrahydroalkylanthraquinone.
7. The method for preparation of hydrogen peroxide according to
claim 1, wherein the organic solvent is a mixture of a nonpolar
solvent, C9-C10 alkylbenzene, and at least one polar solvent
selected from a group consisting of diisobutylcarbinol,
tris-(2-ethylhexyl) phosphate, methylcyclohexyl acetate,
N-butylcaprolactam and tetrabutylurea.
8. A composition for preparation of hydrogen peroxide comprising
2-alkylanthraquinone, 2-tetrahydroalkylanthraquinone and an organic
solvent, wherein 65-95 mol % of the alkyl group of
2-alkylanthraquinone and 2-tetrahydroalkylanthraquinone is amyl and
the remaining 5-35 mol % of the alkyl group is ethyl, and the molar
ratio of 2-alkylanthraquinone to 2-tetrahydroalkylanthraquinone is
from 4:6 to 1:9.
9. The composition for preparation of hydrogen peroxide according
to claim 8, wherein the amyl group comprises tert-amyl and
iso-sec-amyl at a molar ratio of 7:3 to 9:1.
10. The composition for preparation of hydrogen peroxide according
to claim 8, wherein the inert ingredients produced from the side
reaction of 2-alkylanthraquinone is contained in the composition in
an amount of 3-20 wt % of the working solution.
11. The composition for preparation of hydrogen peroxide according
to claim 8, wherein water is further contained in the composition
in an amount of 0.05-0.5 wt % of the working solution.
12. The composition for preparation of hydrogen peroxide according
to claim 8, which comprises 17-34 wt % of 2-alkylanthraquinone and
2-tetrahydroalkylanthraquinone of the working solution.
13. The composition for preparation of hydrogen peroxide according
to claim 8, wherein the organic solvent is a mixture of a nonpolar
solvent, C9-C10 alkylbenzene, and at least one polar solvent
selected from a group consisting of diisobutylcarbinol,
tris-(2-ethylhexyl) phosphate, methylcyclohexyl acetate,
N-butylcaprolactam and tetrabutylurea.
14. The composition for preparation of hydrogen peroxide according
to claim 8, wherein said composition has a specific gravity of
0.89-0.97.
15. The method for preparation of hydrogen peroxide according to
claim 2, wherein the degree of hydrogenation during the reduction
of the working solution is controlled to be 70-100 mol % on the
basis of 2-tetrahydroalkylanthraquinone.
16. The method for preparation of hydrogen peroxide according to
claim 3, wherein the degree of hydrogenation during the reduction
of the working solution is controlled to be 70-100 mol % on the
basis of 2-tetrahydroalkylanthraquinone.
17. The method for preparation of hydrogen peroxide according to
claim 4, wherein the degree of hydrogenation during the reduction
of the working solution is controlled to be 70-100 mol % on the
basis of 2-tetrahydroalkylanthraquinone.
18. The method for preparation of hydrogen peroxide according to
claim 5, wherein the degree of hydrogenation during the reduction
of the working solution is controlled to be 70-100 mol % on the
basis of 2-tetrahydroalkylanthraquinone.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for the
preparation of hydrogen peroxide through a continuous process,
extracting hydrogen peroxide produced from reduction and oxidation
of a working solution and recycling the oxidized working solution
back to the reduction process, wherein the composition of the
working solution, i.e., the composition of 2-alkylanthraquinone and
2-tetrahydroalkylanthraquinone, is optimized to increase the
solubility of the quinones and to improve the reaction rate.
BACKGROUND ART
[0002] At present, hydrogen peroxide is manufactured almost
exclusively for commercial purposes by using alkylanthraquinone as
working material. In the alkylanthraquinone process, a working
solution prepared by dissolving alkylanthraquinones
(alkylanthraquinone and tetrahydroalkylanthraquinone) in an organic
solvent is first reacted in the presence of a catalyst with
hydrogen gas to produce alkylanthrahydroquinone. When the
alkylanthrahydroquinone is oxidized by air or oxygen gas back to
alkylanthraquinone, hydrogen peroxide is produced. Thus produced
hydrogen peroxide is extracted with water, separated, and then
purified. The working solution separated through extraction is
recycled for reduction, oxidation and extraction. This autoxidation
cycle using alkylanthraquinone is well known in the literature
(Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed., 1993,
Vol. 13, pp. 961-995).
[0003] In the autoxidation cycle, the working solution is recycled
repeatedly, during which some of the alkylanthraquinone in the
working solution is slowly converted into
tetrahydroalkylanthraquinone and concentrated in the working
solution. The composition and content of the working solution
greatly affect the productivity of hydrogen peroxide, reaction
rate, easiness of process operation, and production of inert
ingredients from side reactions of alkylanthraquinone.
[0004] There have been many suggestions with respect to the
composition of the working solution, i.e., the kind and proportion
of alkylanthraquinones.
[0005] Korean Patent Publication No. 10-2008-0007102 discloses a
method for preparation of hydrogen peroxide using a working
solution comprising a 2:1 to 8:1 (molar ratio) mixture of
2-alkylanthraquinone (AQ) and 2-tetrahydroalkylanthraquinone
(THAQ), in which 55-90 mol % of the alkyl of the total quinones is
amyl and the remaining 10-45 mol % of the alkyl is ethyl. Although
this patent aims at preparation of hydrogen peroxide with low
impurity content, the productivity of hydrogen peroxide is not so
high because the solubility of the reduced form
alkylanthrahydroquinone (AHQ) is lower than that of
tetrahydroalkylanthrahydroquinone (THAHQ). Further, a higher
proportion of alkylanthraquinone than tetraalkylanthraquinone
during the reduction results in slow hydrogenation reaction rate,
which, in turn, leads to loss of alkylanthraquinone through side
reactions.
[0006] U.S. Pat. No. 6,153,169 uses 2-ethylanthraquinone (EAQ) and
2-amylanthraquinone (AAQ) as well as
2-(4-methyl-3-pentenyl)-anthraquinone (IHEAQ) or
2-(4-methylpentyl)-anthraquinone (IHAQ) as working material. One of
the conditions required for quinone as working material is that it
should be commercially available and inexpensive. However, as
mentioned also in the patent, IHEAQ and IHAQ are commercially
unavailable and should be synthesized for use. Further, the cost of
the raw material is much higher than that of EAQ or AAQ.
[0007] U.S. Pat. No. 6,524,547 suggests the use of a working
solution comprising a mixture of 2-ethylanthraquinone and
2-amylanthraquinone, wherein the content of 2-amylanthraquinone is
10-55 mol % and the molar ratio of tetrahydroalkylanthraquinone to
alkylanthraquinone is at least 1:1. However, because of the high
proportion of 2-ethylanthraquinone, the solubility of
alkylanthraquinone and alkylanthrahydroquinone is low and reaction
rate is slow. Due to the low solubility and slow reaction rate, it
is difficult to improve the productivity of hydrogen peroxide.
[0008] WO 95/28350 discloses a method for preparation of hydrogen
peroxide using an all-tetra system working solution consisting of
2-tetrahydroethylanthraquinone and 2-tetrahydroamylanthraquinone.
However, the productivity of hydrogen peroxide is not high because
the solubility of tetrahydroalkylanthraquinone is lower than that
of alkylanthraquinone. Further, a harsh reaction condition is
required during the oxidation process because the oxidation
reaction rate is retarded. In addition,
tetrahydroalkylanthraquinone is not commercially available, and so
it should be synthesized through an additional process.
[0009] Japanese Patent Laid-open No. Hei 6-191803 discloses a
method for preparation of hydrogen peroxide using a working
solution comprising 3:1 to 6:1 (molar ratio) of 2-amylanthraquinone
(AAQ) and 2-tetrahydroamylanthraquinone (THAAQ). However, because
of high alkylanthraquinone content, this method is associated with
the problem of loss of alkylanthraquinone caused by side reactions
of the alkylanthraquinone during reduction. Further, the
productivity of hydrogen peroxide is not high since the solubility
of reduced alkylanthrahydroquinone (AHQ) is less than that of
tetrahydroalkylanthrahydroquinone (THAHQ).
[0010] U.S. Pat. No. 3,073,680 uses a mixture of
2-ethylanthraquinone (EAQ) and 2-tetrahydroethylanthraquinone
(THEAQ). However, it is impossible to increase the concentration of
EAQ and THEAQ in the working solution because they have low
solubility, which is directly related with the productivity of
hydrogen peroxide.
[0011] U.S. Pat. No. 3,540,847 also uses EAQ and THEAQ as a working
material. However, even though the proportion of THEAQ is higher
than that of EAQ, the productivity of hydrogen peroxide is merely
about 6.5-11 g per liter of the working solution.
DISCLOSURE OF INVENTION
Technical Problem
[0012] The inventors of the present invention have researched to
solve the aforesaid problems. As a result, they found out that the
productivity of the preparation process of hydrogen peroxide can be
improved through the control of the composition of
2-alkylanthraquinone and 2-tetrahydroalkylanthraquinone, the
content of inert ingredients and water, and the degree of
hydrogenation.
Technical Solution
[0013] In an aspect, the present invention provides a method for
preparation of hydrogen peroxide through an anthraquinone recycle
process of reducing and oxidizing a working solution comprising
2-alkylanthraquinone, 2-tetrahydroalkylanthraquinone and an organic
solvent, wherein 65-95 mol % of the alkyl group of
2-alkylanthraquinone and 2-tetrahydroalkylanthraquinone is amyl and
the remaining 5-35 mol % of the alkyl group is ethyl, and the molar
ratio of 2-alkylanthraquinone to 2-tetrahydroalkylanthraquinone is
from 4:6 to 1:9.
[0014] In another aspect, the present invention provides a
composition for preparation of hydrogen peroxide comprising
2-alkylanthraquinone, 2-tetrahydroalkylanthraquinone and an organic
solvent, wherein 65-95 mol % of the alkyl group of
2-alkylanthraquinone and 2-tetrahydroalkylanthraquinone is amyl and
the remaining 5-35 mol % of the alkyl group is ethyl, and the molar
ratio of 2-alkylanthraquinone to 2-tetrahydroalkylanthraquinone is
from 4:6 to 1:9.
ADVANTAGEOUS EFFECTS
[0015] The present invention is advantageous in that the amount of
hydrogen peroxide that can be produced per liter of a working
solution can be enhanced, the reduction time can be reduced, and
the loss of quinone due to side reactions can be minimized through
an optimized proportion of the working material quinone, inert
ingredients and water in the working solution. Especially, the
solubility of the reduced forms alkylanthrahydroquinone and
tetrahydroalkylanthrahydroquinone can be enhanced while the
reaction rate is improved, and the physical properties of the
working solution including specific gravity and viscosity can be
optimized, thereby facilitating the process operation.
BRIEF DESCRIPTION OF DRAWINGS
[0016] The above and other aspects, features and advantages of the
disclosed exemplary embodiments will be more apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which:
[0017] FIG. 1 is a graph showing the reaction rate of reduction
depending on the composition of the working solution.
BEST MODE FOR CARRYING OUT THE INVENTION
[0018] Exemplary embodiments of the present invention will be
described more fully hereinafter.
[0019] The productivity of hydrogen peroxide is proportional to
gp1, that is, the quantity of hydrogen peroxide produced from 1 L
of a reduced working solution. It changes depending on the
concentration of the working material, the degree of hydrogenation,
or the like, and is closely related with the solubility of reduced
alkylanthrahydroquinone. That is to say, a higher solubility of
alkylanthrahydroquinone leads to more hydrogenation, and,
consequently, production of more hydrogen peroxide.
[0020] The working solution is the most important in the
preparation of hydrogen peroxide. Its composition and content
greatly affect the productivity of hydrogen peroxide and process
operation conditions. The general requirements of the
alkylanthraquinone included in the working solution are as follows.
First, the oxidized form, alkylanthraquinone, and the reduced form,
alkylanthrahydroquinone, should have high solubility in the used
organic solvent. Further, it should be chemically stable and the
reaction rate of reduction and oxidation should be high. In
addition, it should not be soluble in water and hydrogen peroxide,
commercially available in large scale, and inexpensive.
[0021] The alkylanthraquinone may be selected from
2-amylanthraquinone, 2-ethylanthraquinone, 2-butylanthraquinone,
2-propylanthraquinone, 2-methylanthraquinone,
2-neopentylanthraquinone, and the like. Especially, the inventors
found out that, rather than a single 2-alkylanthraquinone and its
corresponding 2-tetrahydroalkylanthraquinone, a use of two
2-alkylanthraquinones and their corresponding
2-tetrahydroalkylanthraquinones may provide a superior working
solution.
[0022] In general, 2-amylanthraquinone is advantageous in that it
has high solubility. 2-Ethylanthraquinone has low solubility, and,
thus, is restricted in improving the productivity of hydrogen
peroxide. But, it has a faster reaction rate of reduction than
2-amylanthraquinone, making it advantageous to be applied in the
reduction process. Further, it is inexpensive.
[0023] The inventors found out that a eutectic mixture of two
quinone compounds at a specific proportion may provide a much
higher solubility and improved reaction rate of reduction, as
compared to a single quinone. This means that a combination of
2-ethylanthraquinone and 2-amylanthraquinone at a specific
proportion may provide a maximum productivity of hydrogen
peroxide.
[0024] The alkylanthraquinone used in the present invention
comprises 65-95 mol %, preferably 70-80 mol %, of
2-amylanthraquinone (including 2-tetrahydroamylanthraquinone) and
5-35 mol %, preferably 20-30 mol %, of 2-ethylanthraquinone
(including 2-tetrahydroethylanthraquinone). The aforesaid
proportion corresponds to the optimum molar ratio that provides the
highest solubility and the fastest reduction rate.
[0025] 2-Amylanthraquinone exists as two isomers:
2-tert-amylanthraquinone and 2-iso-sec-amylanthraquinone.
Solubility, generation of side reaction products and reaction rate
of reduction depend on the proportion of the amyl isomers. A
preferred proportion of 2-tert-amylanthraquinone to
2-iso-sec-amylanthraquinone may be from 7:3 to 9:1.
[0026] Another important factor is the proportion of
alkylanthraquinone to tetrahydroalkylanthraquinone, which is
produced from its reaction. Since tetrahydroalkylanthraquinone has
a better solubility in reduced form than alkylanthraquinone, it is
preferable to increase its proportion with respect to the
productivity of hydrogen peroxide. Tetrahydroalkylanthraquinone is
not present in the initial working solution but is formed during
the continuous alkylanthraquinone recycling process. Most of the
formed tetrahydroalkylanthraquinone is
.beta.-tetrahydroalkylanthraquinone, but a small amount of
.alpha.-tetrahydroalkylanthraquinone exists. The mechanism by which
.beta.-tetrahydroalkylanthraquinone is produced is given in
Reaction Scheme 1.
##STR00001##
[0027] Tetrahydroalkylanthraquinone can improve the productivity of
hydrogen peroxide because it has better solubility in reduced form
and provides faster reaction rate of reduction than
alkylanthraquinone [Ind. Eng. Chem. Process Dev. 1983, 22,
150-153]. In particular, due to the side reactions exemplified by
Reaction Scheme 2, alkylanthraquinone is more susceptible to the
loss of working material than tetrahydroalkylanthraquinone
[Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed, 1993,
Vol. 13, pp. 961-995].
##STR00002##
[0028] In order to take advantage of higher solubility of the
reduced form and to minimize loss by the side reactions, it will be
desired to use tetrahydroalkylanthraquinone rather than
alkylanthraquinone. However, tetrahydroalkylanthraquinone is
disadvantageous in that it has lower solubility in oxidized form
than alkylanthraquinone and provides slower oxidation rate in
reduced form.
[0029] Accordingly, for efficient and economical preparation of
hydrogen peroxide, an optimum proportion of alkylanthraquinone and
tetrahydroalkylanthraquinone considering solubility, reaction rate
of reduction, reaction rate of oxidation, and the like needs to be
determined. Through this, the formation of side reaction products
of alkylanthraquinone can be minimized as well.
[0030] The inventors found out that there exists an optimum
proportion of alkylanthraquinone and tetrahydroalkylanthraquinone
which provides the highest solubility of reduced hydroquinones
(alkylanthrahydroquinone and tetrahydroalkylanthrahydroquinone),
less generation of side reaction products and faster reaction rate.
The optimum molar ratio of alkylanthraquinone to
tetrahydroalkylanthraquinone is from 4:6 to 1:9, preferably from
3:7 to 2:8.
[0031] In order to maintain the optimum proportion of
tetrahydroalkylanthraquinone in the working solution, it is
necessary to reduce the tetrahydroalkylanthraquinone produced
continuously through repeated cycles. To this end, the oxidized
working solution is reacted with alumina. The mechanism by which
the proportion of tetrahydroalkylanthraquinone is controlled by
alumina is given in Reaction Scheme 3.
##STR00003##
[0032] In the present invention, the productivity of hydrogen
peroxide per volume of the working solution can be maximized by
increasing the concentration of total quinones in the working
solution within the limit allowed by the physical properties of the
working solution, including solubility, specific gravity,
viscosity, and the like. Particularly, the concentration of total
quinones is restricted by the specific gravity of the working
solution. Above a predetermined concentration, specific gravity
increases, thereby decreasing the distribution coefficient. As a
result, it is difficult to separate hydrogen peroxide from the
working solution during the extraction process. Further, the
increased quinone concentration is accompanied by the increase of
viscosity of the working solution, which results in increased
pressure difference during filtration after the reduction, which,
in turn, results in increased load on the transfer pump and
difficult in process operation. In the present invention, a
preferred concentration of total quinones, i.e. alkylanthraquinone
and tetrahydroalkylanthraquinone, in the working solution is 17-34
wt %, preferably 20-25 wt %.
[0033] The composition of active quinones in the working solution
and the mechanism by which hydrogen peroxide is produced according
to the present invention are given in Reaction Scheme 4.
##STR00004##
[0034] Another important feature of the present invention is that
inert ingredients (inerts), or the side reaction products of
alkylanthraquinone, are included in the working solution. As used
herein, inert ingredients refer to the side reaction products
produced as the working material quinones are degraded while the
working solution is recycled. The inert ingredients are mostly the
substances that cannot produce hydrogen peroxide. For example,
anthrone, dianthrone, or the like are included. The content of the
inert ingredients is determined as the content excluding the
solvent and quinones from the working solution. The formation of
the inert ingredients results in the loss of quinones.
Surprisingly, however, the inventors found out that they increase
the solubility of alkylanthraquinone and its reduced counterpart
alkylanthrahydroquinone in the working solution. Further, the
inventors found out that the inert ingredients improve reaction
rate of reduction, thereby reducing the reduction time. This means
that the presence of the inert ingredients outstandingly contribute
to the improvement of productivity of hydrogen peroxide. But, the
inert ingredients improve the productivity of hydrogen peroxide
only up to a certain level, and they reduce the productivity of
hydrogen peroxide when they are accumulated over a critical level.
Further, they may result in the deterioration of the quality of
hydrogen peroxide because of increased total organic content (TOC).
In addition, they may result in the change of the physical
properties of the working solution, including specific gravity,
viscosity, and so on, thereby negatively affecting the process
operations during catalyst filtration following the reduction and
hydrogen peroxide extraction. In accordance with the present
invention, the inert ingredients are present in the working
solution in an amount of 3-20 wt %, preferably 5-13 wt %.
[0035] For the solvent for preparation the working solution, a
combination of a nonpolar solvent that dissolves alkylanthraquinone
and a polar solvent that dissolves alkylanthrahydroquinone is used.
The requirements for the solvent are as follows. It should dissolve
alkylanthraquinone and alkylanthrahydroquinone well, be chemically
stable under repeated reduction and oxidation, have lower
solubility for water and hydrogen peroxide, and have a difference
of specific gravity of at least 0.03 from water. Further, it should
have low volatility, high boiling point and flashing point, high
hydrogen peroxide distribution coefficient in the solvent-water
system, and low toxicity.
[0036] The organic solvent may be a mixture of a nonpolar solvent,
C.sub.9-C.sub.10 alkylbenzene (including polyalkylbenzene), and at
least one polar solvent selected from a group consisting of
diisobutylcarbinol, tris-(2-ethylhexyl)phosphate, methylcyclohexyl
acetate, N-butylcaprolactam and tetrabutylurea. The polar solvent
is included in the total solvent in an amount of preferably 20-50
wt %, more preferably 25-40 wt %.
[0037] In the present invention, the working solution consisting of
the active quinones, the inert ingredients and the solvent has a
specific gravity of 0.890-0.970, preferably 0.910-0.940, at
30.degree. C.
[0038] The catalyst that can be used in the reduction can be
selected from nickel, palladium, platinum, rhodium, gold, etc.
Palladium, platinum, and so on are preferred. Alumina, alumina
silicate, carbon, silicate (SiO.sub.2), and so on can be used as a
support. In case palladium (Pd) is used as the catalyst, a carbon
support provides good reactivity and selectivity, but after the
reaction it can be difficult to separate the catalyst from the
working solution. A use of the palladium catalyst on an alumina
support provides good reactivity and selectivity and easy
separation from the working solution. Thus, it is appropriated for
industrial-scale production of hydrogen peroxide. Preferably, a
catalyst prepared by 2.0 wt % of palladium on an alumina support
having a particle diameter of 10-100 .mu.m, an average particle
diameter of 40-60 .mu.m and a pore volume of 0.4-1.0 mL/g is
used.
[0039] The inventors found out that the reduction proceeds very
quickly when the working solution contains water within a
predetermined range. The presence of water in the working solution
increases the reactivity and selectivity of the catalyst. It is
contained in the working solution in an amount of 0.05-0.5 wt %,
preferably 0.1-0.35 wt %. When the water content exceeds 0.5 wt %,
the excess water may result in the aggregation of the catalyst
which causes the decrease of the reaction rate of reduction.
[0040] The reduction is performed preferably at 30-80.degree. C.,
more preferably at 40-60.degree. C., under a hydrogen gas pressure
of 7-89 psig, more preferably 15-52 psig, in the presence of the
catalyst. In order to minimize the generation of side reaction
products, which is one of the features of the present invention,
not only the quinone composition but also the degree of
hydrogenation based on the total quinones in the reduction process
is important. In the present invention, the degree of hydrogenation
is within 70-100 mol %, preferably within 80-90 mol % of the total
tetrahydroalkylanthraquinone. When the degree of hydrogenation
exceeds 100 mol % of the total tetrahydroalkylanthraquinone,
alkylanthraquinone may participate in the reaction, thereby leading
to degradation of the active quinones through side reactions.
Meanwhile, when the degree of hydrogenation is below 70 mol %, the
productivity of hydrogen peroxide decreases.
[0041] The oxidation process by which hydrogen peroxide is produced
also greatly affects the productivity of hydrogen peroxide.
Therefore, a quantitative reaction should be performed when the
reduced tetrahydroalkylanthrahydroquinone is oxidized to
tetrahydroalkylanthraquinone. Otherwise, side reaction products
such as epoxide may be formed as inert ingredients during the
oxidation process, and the remaining
tetrahydroalkylanthrahydroquinone what is not completely oxidized
may result in not only decreased productivity but also declined
extraction and reduction efficiencies.
[0042] Preferably, an oxidation tower equipped with a tray having
fine pores is used as oxidation reactor. The oxidation process is
carried out preferably at 30-80.degree. C., more preferably at
40-60.degree. C. An oxygen-containing gas is reacted at a pressure
of preferably 15-150 psig, more preferably 45-104 psig.
[0043] In the method for preparation of hydrogen peroxide through
recycling of the working solution, the inert ingredients produced
from the side reaction of the active quinones are accumulated in
the working solution as time goes by. When the inert ingredients
are accumulated in the working solution by more than 20 wt %, the
quality of hydrogen peroxide and the process operation may be
negatively affected, in addition to the loss of alkylanthraquinone.
Therefore, some of the working solution is regenerated before or
after the reduction in order to convert the inert ingredients into
the active quinones and to remove other impurities. During the
regeneration process, a variety of porous absorbents may be used.
As porous absorbents, .alpha.-Alumina, .gamma.-alumina and
alkalinated .gamma.-alumina are very effective for the regeneration
of the working solution. These aluminas regenerate or adsorb the
inert ingredients in the working solution, and play an important
role in maintaining the proportion of tetrahydroalkylanthraquinone
constant. The regeneration process is carried out preferably at
40-100.degree. C., more preferably at 60-80.degree. C. Of the total
reacted working solution, preferably 5-30%, more preferably 10-20%,
passes through the regeneration process.
MODE FOR THE INVENTION
[0044] The examples will now be described. The following examples
are for illustrative purposes only and not intended to limit the
scope of the present invention. In the examples and comparative
examples, 2-amylanthraquinone is denoted as AAQ,
2-tetrahydroamylanthraquinone as THAAQ, 2-ethylanthraquinone as
EAQ, 2-tetrahydroethylanthraquinone as THEAQ, side reaction
products (inert ingredients) as Inerts,
tetrahydroalkylanthraquinone as THAQ, alkylanthraquinone as AQ,
tetrahydroalkylanthrahydroquinone as THAHQ, alkylanthrahydroquinone
as AHQ, and hydroquinone (tetrahydroalkylanthrahydroquinone and
alkylanthrahydroquinone) as HQ.
Example 1
[0045] In a mixture solvent, alkylanthraquinone and
tetrahydroalkylanthraquinone are dissolved to a total concentration
of 1.26 mol/L, as given in Table 1. As the mixture solvent, a 7:3
(w/w) mixture of alkylbenzene, tetrabuthyurea (solvent A) and a
7:1.5:1.5 (w/w/w) mixture of alkylbenzene, tetrabutylurea and
diisobutylcarbinol (solvent B) are used. Alkylbenzene in the
mixture solvents (solvent A and solvent B) consists of 16 wt %
C.sub.9-alkylbenzene and 84 wt % C.sub.10-alkylbenzene. After
adding the prepared working solution (25 mL), and then 0.3 g of 2%
Pd/Al.sub.2O.sub.3 catalyst to a reactor, the working solution is
reacted with hydrogen gas at 45.degree. C. until hydroquinone (HQ)
is crystallized. After the reaction, the working solution is
separated from the catalyst and HQ crystal, and then a certain
amount of the filtered working solution is added to distilled
water. After oxidation by reacting with oxygen gas, the
concentration of produced hydrogen peroxide is measured to
determine HQ solubility.
[0046] The content of quinones in the working solution is
determined by gas chromatography. HP-1701 column (30 m.times.250
.mu.m.times.1.0 .mu.m) is used, and the content of each component
is quantized from the comparison of area with that of standard
material.
[0047] Hydrogenation uptake refers to the time elapsed until a
specific volume of hydrogen reacts. The volume of hydrogen that
reacts with quinone is measured from the change of the level of the
hydrogen metering tube. The time elapsed until a specific volume of
hydrogen reacts is measured so that 50 mol % of the total quinone
reacts.
[0048] The result is given in Table 1.
TABLE-US-00001 TABLE 1 Example 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7
Solvent A A B A A B A AAQ (mol/L) 0.353 0.265 0.265 0.176 0.302
0.302 0.340 THAAQ (mol/L) 0.529 0.617 0.617 0.706 0.706 0.706 0.794
EAQ (mol/L) 0.151 0.113 0.113 0.076 0.076 0.076 0.038 THEAQ (mol/L)
0.227 0.265 0.265 0.302 0.176 0.176 0.088 Inerts (wt %) 10.5 9.97
9.97 9.97 9.97 9.97 9.97 Mol % ratio (amyl:ethyl) 70:30 70:30 70:30
70:30 80:20 80:20 90:10 Mol % ratio (THAQ:AQ) 60:40 70:30 70:30
80:20 70:30 70:30 70:30 HQ solubility (mol/L) 0.881 0.884 0.899
0.889 0.891 0.903 0.894 H.sub.2O.sub.2 equivalent.sup.1) 30.0 30.1
30.6 30.2 30.3 30.7 30.4 (H.sub.2O.sub.2 g/L) Hydrogenation uptake
50 45 40 40 55 50 60 (min) .sup.1)Theoretical grams of
H.sub.2O.sub.2 that can be produced from 1 L of working
solution
Comparative Example 1
[0049] The following comparative experiment is carried out in order
to compare HQ solubility and reaction rate of reduction for
different quinones and mol % ratios. Alkylanthraquinone and
tetrahydroalkylanthraquinone are dissolved in a 7:3 (w/w) mixture
solvent of alkylbenzene, 16 wt % of C.sub.9-alkylbenzene and 84 wt
% of C.sub.10 alkylbenzene, and tetrabutylurea to a total
concentration of 0.788 mol/L, as in Table 2. Inert ingredients are
not included in the working solution. HQ solubility is measured in
the same manner as Example 1. The result is given in Table 2.
TABLE-US-00002 TABLE 2 Comparative Example 1 1.1 1.2 1.3 1.4 1.5
1.6 1.7 1.8 1.9 AAQ (mol/L) 0.788 0.394 0.552 0.394 0.236 0.118
0.071 0 0 THAAQ 0 0.394 0 0 0 0.118 0.166 0 0 (mol/L) EAQ (mol/L) 0
0 0.236 0.394 0.552 0.276 0.166 0.788 0.394 THEAQ 0 0 0 0 0 0.276
0.386 0 0.394 (mol/L) Mol % ratio 100:0 100:0 70:30 50:50 30:70
30:70 30:70 0:100 0:100 (amyl:ethyl) Mol % ratio 0:100 50:50 0:100
0:100 0:100 50:50 70:30 0:100 50:50 (THAQ:AQ) HQ solubility 0.403
0.409 0.395 0.391 0.370 0.409 0.420 0.304 0.401 (mol/L)
Hydrogenation 255 100 245 235 220 80 75 140 70 uptake (min)
[0050] As seen in Table 2, HQ solubility increases when the
proportion of AAQ is higher. At higher proportion of EAQ, HQ
solubility decreases but reduction (hydrogenation) rate increases.
When the proportion of THAQ is higher than that of AQ, HQ
solubility increases and reduction rate increases.
Example 2
[0051] In order to compare the effect of inert ingredients in the
working solution on HQ solubility and reaction rate of reduction,
HQ solubility is measured in the same manner as Example 1, except
that inert ingredients are not included in the working solution and
that the total quinone concentration is set as 0.788 mol/L
considering the solubility limit. Quinone composition and
solubility measurement result are given in Table 3.
TABLE-US-00003 TABLE 3 Example 2 2.1 2.2 2.3 2.4 2.5 2.6 AAQ
(mol/L) 0.386 0.221 0.166 0.110 0.189 0.213 THAAQ (mol/L) 0.166
0.331 0.386 0.441 0.441 0.496 EAQ (mol/L) 0.166 0.095 0.071 0.473
0.047 0.024 THEAQ (mol/L) 0.071 0.142 0.166 0.189 0.126 0.055 Mol %
ratio (amyl:ethyl) 70:30 70:30 70:30 70:30 80:20 90:10 Mol % ratio
(THAQ:AQ) 30:70 60:40 70:30 80:20 70:30 70:30 HQ solubility (mol/L)
0.504 0.510 0.512 0.513 0.596 0.603 Hydrogenation uptake (min) 140
90 85 80 90 95
[0052] As seen in Table 3, HQ solubility is higher and the reaction
rate of reduction is faster when the mol % ratio of amyl:ethyl is
70:30 or higher and when the mol % ratio of THAQ:AQ is 70:30 or
higher (Examples 2.3-2.6).
[0053] Through Examples 1 and 2 and Comparative Example 1, it can
be seen that the presence of inert ingredients in the working
solution remarkably improves HQ solubility and reaction rate of
reduction. The reaction rate of reduction (hydrogenation uptake)
depending on the compositions of the working solution is shown in
FIG. 1.
Example 3
Stability of Working Solution
[0054] A working solution is prepared by dissolving AAQ (0.143
mol/L), THAAQ (0.366 mol/L), EAQ (0.075 mol/L) and THEAQ (0.140
mol/L) in a 7:3 (w/w) mixture solvent of alkylbenzene (16 wt % of
C.sub.9 alkylbenzene and 84 wt % of C.sub.10 alkylbenzene) and
tetrabutylurea. To the resultant working solution, 2.0 wt %
catalyst (2.0% Pd/Al.sub.2O.sub.3) is added in a pressurized
reactor, and reaction is performed for 72 hours at 65.degree. C.,
under a hydrogen gas of 80 psig. The catalyst is removed from the
reaction mixture, and the reduced working solution is oxidized to
produce hydrogen peroxide. After removing hydrogen peroxide, the
composition of the working solution is analyzed by gas
chromatography. The result is given in Table 4.
Comparative Example 2
[0055] A working solution comprising AAQ (0.374 mol/L) and THAAQ
(0.362 mol/L) is prepared. Stability of the working solution is
measured in the same manner as Example 3. The result is given in
Table 4.
Comparative Example 3
[0056] A working solution comprising AAQ (0.377 mol/L), THAAQ
(0.150 mol/L), EAQ (0.145 mol/L) and THEAQ (0.061 mol/L) is
prepared. Stability of the working solution is measured in the same
manner as Example 3. The result is given in Table 4.
TABLE-US-00004 TABLE 4 Comparative Comparative Example 3 Example 2
Example 3 Before After Before After Before After AAQ (mol/L) 0.143
0.007 0.374 0.015 0.377 0.012 THAAQ (mol/L) 0.366 0.499 0.362 0.688
0.150 0.463 EAQ (mol/L) 0.075 0.004 0 0 0.145 0.020 THEAQ (mol/L)
0.140 0.192 0 0 0.061 0.165 Total quinones 0.724 0.701 0.736 0.702
0.733 0.660 (mol/L) Mol % ratio 74:26 75:25 100:0 100:0 75:25 75:25
(amyl:ethyl) Mol % ratio 70:30 99:1 49:51 98:1 29:71 96:4 (THAQ:AQ)
Inerts (wt %) 9.85 10.34 8.40 9.25 9.70 11.61 Increase of Inerts
0.49 0.85 1.91 (%)
[0057] When comparing the working solution according to the present
invention (Example 3) with those of the working solution comprising
only AAQ and THAAQ (Comparative Example 2) and the working solution
with a different THAQ:AQ mol % ratio (Comparative Example 3),
Example 3 exhibits less production of inert ingredients under harsh
conditions. Thus, it can be seen that the working solution
according to the present invention has superior stability.
Example 4
Hydrogenation Uptake Depending on Water Content in Working
Solution
[0058] A working solution is prepared by dissolving AAQ (0.143
mol/L), THAAQ (0.366 mol/L), EAQ (0.075 mol/L), THEAQ (0.140 mol/L)
and Inerts (9.85 wt %) in a 7:3 (w/w) mixture solvent of
alkylbenzene (16 wt % of C.sub.9 alkylbenzene and 84 wt % of
C.sub.10 alkylbenzene) and tetrabutylurea. Water content in the
prepared working solution is set as 0.1 wt %, 0.25 wt % and 0.35 wt
%, using deionized water. The water content of the working
solutions is measured using a Karl Fischer meter. Hydrogenation
uptake is measured using the prepared working solutions.
Comparative Example 4
[0059] Working solutions with the same composition as Example 4 and
water contents of 0 wt % and 1.0 wt % are prepared. Hydrogenation
uptake is measured in the same manner as Example 4.
TABLE-US-00005 TABLE 5 Comparative Example 4 Example 4 4.1 4.2 4.3
4.1 4.2 Water content (wt %) 0.1 0.25 0.35 0 1.0 Hydrogenation
uptake (min) 30 27 28 45 120
[0060] As seen from Example 4 and Comparative Example 4,
hydrogenation proceeds faster when there exists a certain quantity
of water in the working solution. If the water content is 1.0 wt %
or above, as in Comparative Example 4.2, aggregation of the
catalyst occurs, thereby resulting in slow hydrogenation uptake
(reaction rate of reduction).
Example 5
[0061] Using a small-scale apparatus for continuous preparation of
hydrogen peroxide equipped with reduction, oxidation, extraction
and recycling units, hydrogen peroxide is produced for one month
while circulating a working solution. A working solution that has
been used for preparation of hydrogen peroxide for a long period
time in a plant is used. The working solution is prepared by
dissolving AAQ (0.145 mol/L), THAAQ (0.366 mol/L), EAQ (0.168
mol/L), THEAQ (0.168 mol/L) and inert ingredients (9.85 wt %) in a
7:3 (w/w) mixture solvent of benzene and tetrabutylurea. The total
amount of the working solution is 30 L and the circulation volume
is controlled to be 15 L/hr. Operation is carried out so that the
degree of hydrogenation is 90% based on the total
tetrahydroalkylanthraquinone. Detailed description of each process
is given below.
[0062] Reduction
[0063] The working solution is introduced into a reduction reactor
equipped with a stirrer, a temperature-controllable jacket and a
catalyst filtering apparatus. 2.0% Pd/Al.sub.2O.sub.3 catalyst with
an average particle size of 50 m is added in an amount of 2.0 wt %
based on the working solution, and reaction is carried out
continuously while maintaining reaction temperature at 45.degree.
C. and hydrogen gas pressure at 20 psig.
[0064] Oxidation
[0065] The reduced working solution and air are reacted in a
multi-stage counter-current oxidation tower equipped with a finely
perforated tray while maintaining temperature at 55.degree. C. and
pressure at 80 psig.
[0066] Extraction
[0067] Hydrogen peroxide is extracted from the oxidized working
solution using a common extraction apparatus. After the extraction
process, the oxidized working solution is recycled to the reduction
process.
[0068] Regeneration
[0069] A regeneration process is omitted in order to observe the
change of the composition of the working solution.
[0070] Change of the composition and physical properties of the
working solution is observed after a month of production of
hydrogen peroxide. The result is given in Table 6.
[0071] Specific gravity of the working solution is measured using a
chain balance. Viscosity of the working solution is determined as
follows. A sample is put in a viscometer tube maintained at
constant temperature in a water bath, and the time required to pass
through the narrow tube is measured. The viscosity is calculated
from the measured time and the specific gravity.
Example 6
[0072] Hydrogen peroxide is produced in the same manner as Example
5 except that the working solution comprises AAQ (0.142 mol/L),
THAAQ (0.531 mol/L), EAQ (0.028 mol/L), THEAQ (0.11 mol/L) and
inert ingredients (8.4 wt %). Change of the composition and
physical properties of the working solution is observed after a
month of production of hydrogen peroxide. The result is given in
Table 6.
Comparative Example 5
[0073] Hydrogen peroxide is produced in the same manner as Example
5 except that the working solution comprises AAQ (0.337 mol/L),
THAAQ (0.143 mol/L), EAQ (0.171 mol/L), THEAQ (0.072 mol/L) and
inert ingredients (9.7 wt %). Operation is carried out in the same
manner as Example 5, without considering degree of hydrogenation
based on the quantity of tetrahydroalkylanthraquinone. Change of
the composition and physical properties of the working solution is
observed after a month of production of hydrogen peroxide. The
result is given in Table 6.
Comparative Example 6
[0074] Hydrogen peroxide is produced in the same manner as Example
5 except that the working solution comprises AAQ (0.018 mol/L),
THAAQ (0.044 mol/L), EAQ (0.201 mol/L), THEAQ (0.461 mol/L) and
inert ingredients (7.55 wt %). Operation is carried out while
maintaining the maximum degree of hydrogenation allowed by the
solubility limitation. Change of the composition and physical
properties of the working solution is observed after a month of
production of hydrogen peroxide. The result is given in Table
6.
TABLE-US-00006 TABLE 6 Comparative Comparative Example 5 Example 6
Example 5 Example 6 One One One One month month month month Start
later Start later Start later Start later AAQ (mol/L) 0.143 0.142
0.134 0.130 0.377 0.329 0.018 0.017 THAAQ (mol/L) 0.366 0.368 0.546
0.548 0.150 0.174 0.044 0.043 EAQ (mol/L) 0.075 0.071 0.024 0.022
0.145 0.137 0.201 0.200 THEAQ (mol/L) 0.140 0.141 0.108 0.109 0.061
0.067 0.461 0.461 Total quinones (mol/L) 0.724 0.722 0.814 0.809
0.732 0.700 0.724 0.721 Inerts (wt %) 9.85 9.87 8.40 8.46 9.70
10.35 7.55 7.58 Water content (wt %) 0.23 0.25 0.21 0.24 0.22 0.24
0.23 0.25 Mol % ratio (amyl:ethyl) 74:26 74:26 86:14 86:14 72:25
74:26 10:90 9:91 Mol % ratio (THAQ:AQ) 70:30 71:29 81:19 81:19
29:71 35:65 70:30 71:29 Specific gravity (35.degree. C.) 0.9371
0.9372 0.9455 0.9457 0.9370 0.9368 0.9305 0.9302 Viscosity
(35.degree. C.) 4.31 4.33 4.82 4.84 4.25 4.26 4.17 4.16
Distribution coefficient 81.7 81.9 76.7 75.3 77.1 75.3 71.4 69.8
H.sub.2O.sub.2 (g/L) produced per 1 L 15.2 20.1 14.2 12.5 of
working solution
[0075] When comparing Example 5 and Comparative Example 5 (mol %
ratio of THAQ:AQ is different), the quantity of hydrogen peroxide
produced per 1 L of working solution for one month is almost
similar. However, Comparative Example 5 shows significantly
increased quantity of inert ingredients, side reaction products of
active quinones. This indicates that, in Comparative Example 5,
alkylanthraquinone participates in reduction, thereby facilitating
side reactions of active quinones. Examples 5 and 6 show little
changes in specific gravity, viscosity and distribution
coefficient, which are related to easiness of operation.
[0076] In spite of high productivity of hydrogen peroxide, Example
6 exhibits fewer side reaction products of quinones since only
tetrahydroalkylanthraquinone participates in reduction. Comparative
Example 6 exhibits lower productivity of hydrogen peroxide because
the degree of hydrogenation (reduction) cannot be increased due to
low HQ solubility of the working solution.
[0077] While the exemplary embodiments have been shown and
described, it will be understood by those skilled in the art that
various changes in form and details may be made thereto without
departing from the spirit and scope of the invention as defined by
the appended claims.
[0078] In addition, many modifications can be made to adapt a
particular situation or material to the teachings of this
disclosure without departing from the essential scope thereof.
Therefore, it is intended that this invention not be limited to the
particular exemplary embodiments disclosed as the best mode
contemplated for carrying out this invention, but that this
invention will include all embodiments falling within the scope of
the appended claims.
* * * * *